1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device having column spacers and a method of fabricating a liquid crystal display device having column spacers.
2. Discussion of the Related Art
In general, a liquid crystal display (LCD) device makes use of optical anisotropy and polarization properties of liquid crystal molecules. The liquid crystal molecules have an orientation alignment that results from their long thin shape. The orientation of the liquid crystal molecules can be controlled by application of an electric field to the liquid crystal molecules. Accordingly, as an intensity of the applied electric field changes, the orientation of the liquid crystal molecules also changes. Since incident light passing through a liquid crystal material is refracted due to an orientation of the liquid crystal molecules resulting from the optical anisotropy of the aligned liquid crystal molecules, an intensity of the incident light can be controlled and images can be displayed.
FIG. 1 a schematic view of a related art LCD device.
In FIG. 1, the LCD device 11 includes upper and lower substrates 5 and 22. A black matrix 6, a color filter 8 having red, green and blue sub-color filters, and a common electrode 18 disposed above the color filter 8, are formed on the upper substrate 5. A pixel region P is defined in the upper and lower substrates 5 and 22, and a pixel electrode 17 is disposed on the pixel region P. In addition, an array structure, which includes a thin film transistor T, is formed on the lower substrate 22. A liquid crystal layer 14 is interposed between the upper and lower substrates 5 and 22.
The lower substrate 22 is commonly referred to as an array substrate, where thin film transistors T are arranged in a matrix configuration, and gate and data lines 13 and is that cross each other are formed, with the thin film transistors T located near the crossings. The pixel region P is defined by the gate and data lines 13 and 15, and a transparent conductive material such as indium-tin-oxide (ITO) having a relatively high transmittance is used as the pixel electrode 17 on the pixel region P. A storage capacitor CST is formed on the gate line 13 and is connected to the pixel electrode 17 in parallel. At this time, a portion of the gate line 13 is utilized as a first electrode of the storage capacitor CST, and a second electrode 30 of the storage capacitor CST is formed by using the same layer and the same material as the data line 15. A signal of the pixel electrode 17 is applied to the second electrode 30 of the storage capacitor CST, which is electrically connected to the pixel electrode 17.
The LCD further includes a column spacer (not shown) between the upper and lower substrates 5 and 22 in order to maintain a cell gap that is defined as a thickness of the liquid crystal layer 14.
FIG. 2 is a cross-sectional view illustrating an LCD device having a column spacer according to the related art.
In FIG. 2, a black matrix 220 having an open portion 225 is formed on a substrate 210. The open portion 225 includes first to third sub-open portions 225a, 225b and 225c. Although not shown, the substrate 210 includes a pixel region having red, green and blue sub-pixel regions, and each of the first to third sub-open portions 225a, 225b and 225c corresponds to each of the red, green and blue sub-pixel regions.
A color filter layer 230 is formed on the black matrix 220. The color filter layer 230 includes red, green and blue sub-color filters 230a, 230b and 230c. Each of the red, green and blue sub-color filters 230a, 230b and 230c corresponds to each of the first to third sub-open portions 225a, 225b and 225c. 
In addition, an overcoat layer 240 is formed on an entire surface of the color filter layer 230 in order to planarizes the substrate 210 having the color filter layer 230, and a plurality of column spacers 250 are formed on the overcoat layer 240 in order to maintain a cell gap between the substrate 210 and the other substrate (not shown).
This substrate for the LCD device according to the related art requires a plurality of mask processes to be manufactured. Hereinafter, a method of fabricating a substrate for a liquid crystal display device according to the related art will be explained with reference to accompanying drawings.
FIGS. 3A to 3G are cross-sectional views illustrating a method for fabricating a substrate for a liquid crystal display device according to the related art.
In FIG. 3A, a black matrix 220 is formed by coating a light shielding material layer on a substrate 210 and by patterning the light shielding material using a patterning process such as a mask process, which includes exposure and developing processes. The black matrix 220 having first to third sub-open portions 225a, 225b and 225c are formed by the patterning process. Next, the black matrix 220 is subject to a heat treatment for curing. Although not shown, the first to third sub-open portions 225a, 225b and 225c correspond to red, green and blue sub-pixel regions, respectively, and the black matrix 220 is located in a non-pixel region surrounding the pixel region.
Next, in FIG. 3B, a red color resin 229 is coated over the substrate 210 having the black matrix 220. The red color resin 229 is selected from photosensitive materials.
In FIG. 3C, the red color resin layer 229 is patterned into a red sub-color filter 230a in the first sub-open portion 225a, and then is subject to a heat treatment for curing. The patterning step for the red sub-color filter 230a is a mask process, which includes exposure and developing processes.
Next, in FIG. 3D, a green sub-color filter 230b is formed in the second sub-open portion 225b by coating a green resin material layer and pattering the green resin material layer using a mask process.
In FIG. 3E, a blue sub-color filter 230c is formed in the third sub-open portion 225c by coating a blue resin material layer and patterning the blue resin material layer using a mask process. The red, green and blue sub-color filters 230a, 230b and 230c constitute a color filter layer 230.
In FIG. 3F, an overcoat layer 240 is formed by coating a transparent organic material on an entire surface of the color filter layer 230 and by pattering the transparent organic material layer. Next, the overcoat layer 240 is also subject to a heat treatment for curing.
Meanwhile, because a sealant (not shown) for attaching two substrates (upper and lower substrates) is located along edges of the substrate 210, a mask process for the overcoat layer 240 is added to form the overcoat layer 240 inside the sealant.
Next, in FIG. 3G, a plurality of column spacers 250 are formed by coating a photosensitive organic material on the overcoat layer 240 and by patterning the photosensitive organic material layer using a mask process. Next, a heat treatment is performed to cure the column spacer 250.
As explained process above, a method for fabricating the LCD device according to the related art is formed by coating, exposure, developing and curing processes to form the black matrix, the color filter layer, the overcoat layer and the column spacers. Therefore, the number of process steps for fabricating the LCD device becomes high. Specifically, as the number of mask steps increases, the production cost increases. Moreover, it raises such problems as device defects, low production yield, and the like.